This description relates to semiconductor electronic devices, and, more particularly, to a method and system for providing over-voltage protection using semiconductor devices.
Metal Oxide Varistors (MOV) are passive over-voltage protection devices that are used widely in electronic circuits. MOVs have a high energy absorption capability and can therefore withstand currents of, for example, several kilo Amperes (kA). However, MOVs also have several disadvantages such as, but, not limited to: (a) a relatively high resistance due to relatively low alpha (α) values; (b) a high voltage drop, which exposes any sensitive electronic circuits being protected, to voltages that can be detrimental for the circuit health; (c) a limited life, because at a peak rated current of the MOV, the MOV is rated for a limited number of over-voltage events at the rated breakdown voltage as the dielectric material of which the MOV is made degrades substantially each time high currents flow through it; (d) a relatively large active area requirement due to a low current density of the MOV material to enable them to carry a relatively high current; (e) a relatively high capacitance; and (f) a potential flammability/explosivity hazard at certain fault conditions because of potting materials that MOVs contain.
Although silicon devices have been used for preventing sensitive electronics coupled in parallel to transient voltage suppressor (TVS) devices from being subjected to voltage spikes caused by, for example, lightning strikes and being damaged, they are not suitable for high temperature operation. Silicon devices tend to leak higher current as temperature increases, with the current reaching unacceptably high values in ambient temperatures greater than approximately 150° C., which makes them unsuitable to be used in ambient temperatures of 225° C. or more needed for aviation applications requiring core engine-mounted electronics such as distributed engine control or for large current carrying applications where I2R losses can account for the high temperature in the device. Moreover, known TVS devices typically are packaged using epoxy encapsulation. Epoxy packaging tends to induce large thermal strains within the TVS device structure above approximately 185° C. and to begin to decompose.